Thursday, February 22, 2018

[Cnidaria • 2018] A Simple Molecular Technique for Distinguishing Species reveals Frequent Misidentification of Hawaiian Corals in the Genus Pocillopora

colonies of Pocillopora spp. from O‘ahu, Hawai‘i;
(B–D) Pocillopora ligulata(F–I) P. meandrina and (K–M) P. eydouxi

Johnston​, Forsman & Toonen, 2018.
 DOI:  10.7717/peerj.4355 

Species within the scleractinian genus Pocillopora Lamarck 1816 exhibit extreme phenotypic plasticity, making identification based on morphology difficult. However, the mitochondrial open reading frame (mtORF) marker provides a useful genetic tool for identification of most species in this genus, with a notable exception of P. eydouxi and P. meandrina. Based on recent genomic work, we present a quick and simple, gel-based restriction fragment length polymorphism (RFLP) method for the identification of all six Pocillopora species occurring in Hawai‘i by amplifying either the mtORF region, a newly discovered histone region, or both, and then using the restriction enzymes targeting diagnostic sequences we unambiguously identify each species. Using this approach, we documented frequent misidentification of Pocillopora species based on colony morphology. We found that P. acuta colonies are frequently mistakenly identified as P. damicornis in Kāne‘ohe Bay, O‘ahu. We also found that P. meandrina likely has a northern range limit in the Northwest Hawaiian Islands, above which P. ligulata was regularly mistaken for P. meandrina.

Figure 3: Images of Pocillopora ligulata colonies, (A)–(E); P. meandrina colonies, (F)–(J); and P. eydouxi colonies, (K)–(O) from O‘ahu, Hawai‘i. 

Figure 1: Pocillopora species composition across the Hawaiian Islands for samples collected from colonies demonstrating P. meandrina morphology. The size of the pie chart is proportional to the number of individuals sampled per island. Pocillopora species are represented by different colors, specifically: P. meandrina, light yellow; P. eydouxi, dark yellow; P. ligulata, light blue; and P. verrucosa, dark blue.

Here, we present an assay that allows rapid and unambiguous identification of all six species of Pocillopora present in Hawai‘i, which we hope will work anywhere these species are found. We present two cases where samples identified morphologically were misidentified to highlight the utility of this approach. Taxonomic confusion can impact a wide range of studies and the ability to rapidly and cost-effectively distinguish among species of Pocillopora will benefit future studies of population structure, ecology, biodiversity, evolution and conservation in this challenging genus.

Erika C. Johnston​, Zac H. Forsman and Robert J. Toonen. 2018. A Simple Molecular Technique for Distinguishing Species reveals Frequent Misidentification of Hawaiian Corals in the Genus Pocillopora.  PeerJ. 6:e4355.  DOI:  10.7717/peerj.4355

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